1. Field of the Invention
The present invention relates generally to airfoils and, more specifically, to airfoil shapes used in compressors, e.g., as part of gas turbines.
2. Description of Related Art
A compressor is a machine which accelerates gas particles to, ultimately, increase the pressure of a compressible fluid, e.g., a gas, through the use of mechanical energy. Compressors are used in a number of different applications, including operating as an initial stage of a gas turbine engine. Among the various types of compressors are the so-called centrifugal compressors, in which mechanical energy operates on gas input to the compressor by way of centrifugal acceleration, e.g., by rotating a centrifugal impeller (sometimes also called a “rotor”) by which the compressible fluid is passing, and axial compressors which have, as each stage, a drum having a number of annular airfoil rows (blades) attached thereto. The airfoils attached to the drum rotate between a similar number of stationary airfoil rows attached to a stationary casing. More generally, axial and centrifugal compressors can be said to be part of a class of machinery known as “turbo machines” or “turbo rotating machines”.
In a gas turbine engine, many system requirements should be met at each stage of a gas turbine's flow path section to meet design goals. These design goals include, but are not limited to, overall improved efficiency and airfoil loading capability. For example, and in no way limiting of the invention, a blade of a compressor stator should achieve thermal and mechanical operating requirements associated with the particular stage in which it is located. Similarly, and also as a purely illustrative example, a blade of a compressor rotor should also achieve thermal and mechanical operating requirements associated with the particular stage of the gas turbine in which it is located.
In particular, it would be desirable to ensure that the surfaces of such blades are shaped so that their resonance frequencies are tuned to accommodate operating characteristics of the turbo machines as a whole.